This invention relates to a wheel bearing assembly with an automotive brake rotor.
There are automotive wheel bearing assemblies used for driving wheels and non-driving wheels. FIG. 7 shows a conventional wheel bearing assembly for a driving wheel. It comprises an outer member 63 provided with double-row raceways 61 and 62 on its inner periphery, an inner member 66 provided with double-row raceways 64 and 65 opposite the raceways 61 and 62 of the outer member 63, and double-row rolling elements 67 and 68 disposed between these opposed raceways 61, 64 and 62, 65.
A tubular portion 69 to be mounted to an axle side is provided at the inner periphery of the inner member 66, while a flange 70, to which is mounted a wheel, is provided at the outer peripheral side of inner member 66. Also, on the outer member 63, a flange 71 to be mounted to a vehicle body side is provided. The raceway 64 is on the outer side with respect to the center of the vehicle body, and is formed directly on the outer periphery of the tubular portion 69. The raceway 65 is on the side near to the center of the vehicle body (i.e., the inner side), and is formed on a separate inner ring member 72.
An automobile manufacturer will mount a disk rotor 73 for a separate brake part to the flange 70 by bolts 74, and a wheel is adapted to be mounted by bolts 75. As a material for the disk rotor 73, an FC-family cast iron, which is superior in seizure resistance, is ordinarily used. In the case of a drum brake, which is often used for a non-driving wheel, a drum such as a brake rotor is mounted to the flange 70.
As described above, with a conventional wheel bearing assembly, since it is necessary to mount a brake rotor (which is a separate part) to the wheel-mounting flange of the inner member, a great deal of work is needed for mounting and runout adjustment, and the number of parts is large.
Any runout of the brake rotor can cause vibrations or squeal during braking, or uneven wear of the brake rotor itself or the brake pad, thus worsening the vibration or squeal. Heretofore, automobile manufacturers to whom the wheel bearing assemblies are supplied have carried out the runout adjustment of the brake rotor, but such an adjustment is very troublesome and inefficient.
An object of this invention is therefore to provide a wheel bearing assembly which does not need mounting or runout adjustment of a brake rotor, and which has a small number of parts.
According to this invention, a wheel bearing assembly includes an outer member to be mounted to a vehicle body and formed with double-row raceways on the inner periphery thereof, and an inner member having at its inner peripheral end a tubular portion to be mounted to an axle and formed with double-row raceways opposite to the respective raceways of the outer member. Double-row rolling elements are arranged between the respective opposing raceways of the outer member and the inner member. The inner member has an integrally-formed wheel-mounting flange and an integrally-formed brake rotor so that the brake rotor and the flange are both integrally-formed portions of the inner member (i.e., the inner member with the wheel-mounting flange and the brake rotor is formed as a single unit).
By integrally forming the brake rotor with the wheel-mounting flange, it is unnecessary to mount a brake rotor and adjust runout, and the parts for mounting the brake rotor are eliminated.
By forming the double-row raceways of the inner member on one or two separate ring members, it is possible to use different materials for the inner member, which is formed integrally with a brake rotor, and the ring members. By using an FC-family cast iron (which is superior in seizure resistance) for the inner member, and a tough bearing steel for the ring members, it is possible to let excellent brake function and bearing function coexist with each other, reduce the amount of expensive bearing steel used and reduce the material cost.
The separate ring member may be divided into a first ring member and a second inner ring member, and the outer raceway with respect to the center of the vehicle body may be provided on the outer peripheral surface of the first outer ring member while the inner raceway with respect to the center of the vehicle body is provided on the outer peripheral surface of the second inner ring member. The first outer ring member is pressed onto the outer peripheral surface of the tubular portion of the inner member, and the second inner ring member may be a constant-velocity joint or a spindle mounted to the tubular portion. With this arrangement, it is possible to supply a constant-velocity joint or a spindle (which is a part to be coupled with an axle) to a customer, mounted beforehand on the wheel bearing assembly.
By forming the inner row of raceway of the second inner ring member on a separate inner ring member, it is possible to make only the separate inner ring member of an expensive bearing steel, ensure an excellent bearing function and reduce the material cost.
By mounting the second inner ring member to the tubular portion of the inner member by caulking, it is possible to reduce the weight compared with the conventional nut-tightening. Also, it is possible to more rigidly fix a constant-velocity joint or a spindle to the tubular portion of the inner member and to stably retain the raceways formed on their outer peripheral surfaces.
By integrally forming the vehicle body-mounting flange on the outer member, it is possible to supply it to a customer with a knuckle (a part to be coupled with the vehicle body) that is mounted beforehand on the wheel bearing assembly.
By restricting the maximum amount of runout of the braking surface of the brake rotor to within a predetermined value, it is possible to suppress any runout of the braking surface of the brake rotor during rotation. Also, troublesome runout adjustment at an automobile manufacturer can be eliminated. Thus it is possible to avoid the generation of vibration or squeak during braking and to prevent uneven wear of the brake rotor itself and the brake pad.
The maximum amount of runout of the braking surface of the brake rotor should be 100 xcexcm. If it is 50 xcexcm, the beneficial effect will be increased.